Aneurysms and/or dissections may occur in blood vessels, and most typically occur in the aorta and peripheral arteries. Depending on the region of the aorta involved, the aneurysm may extend into areas having vessel bifurcations or segments of the aorta from which smaller “branch” arteries extend. Various types of aortic aneurysms may be classified on the basis of the region of aneurysmal involvement. For example, thoracic aortic aneurysms include aneurysms present in the ascending thoracic aorta, the aortic arch, and branch arteries that emanate therefrom, such as subclavian arteries, and also include aneurysms present in the descending thoracic aorta and branch arteries that emanate therefrom, such as thoracic intercostal arteries and/or the suprarenal abdominal aorta and branch arteries that emanate therefrom, which could include renal, superior mesenteric, celiac and/or intercostal arteries. Lastly, abdominal aortic aneurysms include aneurysms present in the aorta below the diaphragm, e.g., pararenal aorta and the branch arteries that emanate therefrom, such as the renal arteries.
For patients with aneurysms of the aorta, surgery to replace the aorta may be performed where a portion of the aorta is replaced with a fabric substitute in an operation that uses a heart-lung machine. In such a case, the aneurysmal portion of the aorta is removed or opened and a substitute lumen is sewn across the aneurysmal portion to span it. Such surgery is highly invasive, requires an extended recovery period and, therefore, cannot be performed on individuals in fragile health or with other contraindicative factors.
When aneurysms are near branch vessels or extend into branch vessels, stent-grafts are used with fenestrations, external couplings, or other means for branch stent-grafts to be deployed into the branch vessels. The location of such fenestrations or external couplings may be critical so as not to block branch vessels. Further, when aneurysms are near branch vessels, the “landing zone” for the stent-graft may be limited such that accurate placement of the stent-graft is critical. Thus, it is desirable to be able to accurately position the stent-graft. However, stents of the stent-graft are normally designed to expand to a size larger than the target vessel to ensure apposition against the vessel wall. Thus, re-positioning the stent-graft after deployment is difficult. It is thus desirable to partially deploy the stent-graft to a diameter larger than the delivery catheter diameter, but smaller than the fully deployed diameter to enable re-positioning of the stent-graft.
Further, when aneurysms are located near branch vessels, it may be desirable to deploy the stent-graft to a diameter smaller than the fully deployed diameter in the main vessel in order to perform various actions to cannulate the branch vessels prior to completely deploying the stent-graft. Partially deploying the stent-graft allows for space outside of the stent-graft within the main vessel to perform such actions.
Devices to maintain stent-grafts in a partially deployed configuration after release from a catheter have been contemplated. However, with current devices, the stent-graft may jump out of position when the stent-graft is deployed. Accordingly, it would be desirable to minimize any movement of the stent-graft when fully deploying the stent graft by releasing the circumferentially constraining sutures.